Siderite

Refractive Index: 1.8700
Abbe Number: 35.0
Crystal System: Isotropic (cubic)
Formation: Natural
Dispersion Data: Approximate (from n, V)
Fits: 1

Refraction Fits

Fit #1— Cauchy from (n_D, V_D)

Cauchy approximation

Valid 0.38–0.78 µm

$n$

n

= 1.8700

V_{D}

= 35.0

n (λ) = 1.8325 + 0.013012/ λ^{2}

Fe carbonate. GIA dispersion 0.035. Source: GIA / Winchell / Liddicoat gemological tables.

Absorption Specimens

Portugal, Castelo Branco District, Covilhã (Panasqueira Mine)

Portugal, Castelo Branco District, Covilhã (Panasqueira Mine)